Space heater



FIG. 1 is a top front perspective view of a space heater, showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a left end elevational view thereof;

FIG. 5 is a right end elevational view thereof. 

The ornamental design for a space heater, as shown. 